Sydney is about 6 times bigger than Chicago.

Chicago is approximately 590 sq km, while Sydney (the 30 councils of metropolitan Sydney, without the Blue Mountains, Hawkesbury, Wollondilly and the Central Coast) is approximately 3,810 sq km, making Sydney 546% larger than Chicago.
Tip: This to-scale comparison of Chicago vs. Sydney uses the Mercator projection, which distorts the size of regions near the poles.
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